So, if I were to use a slide with a depression in it for viewing pond water, the importance of the thickness of the cover glass wouldn’t matter much, even with 100x oil objective? I’ll fill the depression overflowingly, then put the cover glass so that excess water leaves, while not having any air bubbles trapped inside. This should negate the air refractive index, but then again, the refractive index of the water is different (I’m pretty sure on that one). This is all conjecture, as I don’t have the microscope and slides just yet. So in the end, the best way to view pond water is not with a well, but only a flat slide with only the thin layer of water under the cover glass. Sorry, I’m inexperienced, and also thinking “aloud”.

Take care,
Huy

Yes, cover slip thickness still matters, even if the index between cover slip and oil is the same, if the specimen is mounted in a medium with a different refractive index and is located not directly beneath the cover slip.

Explained here:
http://www.microscopyu.com/articles/formulas/formulascoverslipcorrection.html

Oliver.

I’m curious about the affect on very high NA oil coupled objectives (100x 1.3NA) of not only the thickness changing, but also the index. For example will a fused silica coverslip with index 1.48 affect aberrations enough to worry about the index difference (index oil is 1.52 index)?

I notice that our oil coupled objectives are still marked for .17mm coverslip thickness, but does thickness matter if the index isn’t changing from oil to the glass?

http://www.microscopyu.com/articles/formulas/formulascoverslipcorrection.html

Many older (circa early to mid 1950′s microscopes) microscopes have an adjustment knob for the body-tube itself of the microscope.

And of course as you here noted, specific microscopes have ‘a correction collar’ right on the objective barrel.

My questions…how did these oldtime microscopists adjust either ‘adjustment knob or barrel’? Did they do it by quality of a certain stardard image they ‘expected to see’ with that setup? I can not imagine how you can ‘gap-guage’ a delicate glass coverslip with a metal shop caliper micrometer. I do have old ( circa late 1800′s-early 1900′s booklets which came with such vintage scopes…I should dig these vintage manuals out and read! It just seems to me that the optical index of the mounting sandwich a specimen is within is variable to a degree far greater than the variation in coverslip thickness ( yet the cover slip thickness as you say, it varies too)…and admist all this ‘variable media’…you add the awkwardness of ‘hand held micrometer calipers’ to read (without variation!?) the thickness of a delicate glass coverslip…it seems I miss an aspect of the skilled vintage microscopist technique for adjusting both the microscope-tube compensator-knob, and that correction-collar adjustment on the objectives which have such a critical correction device.

And yes, these questions of mine are practicle for me…as I have both vintage microscopes with that body-tube length adjustment knob, the vintage manuals which talk about adjustment for coverslip thickness, and always wondering when : size 1/2 coverslips are needed, I wonder when those very thin coverslips are needed?

Again, no need to reply…perhaps I can tidy up my use of images of my vintage stand, it’s vintage manual describing it’s adjustments, and offer this wonderment as a thread in your forums? I can’t wait for your online magazine to come out soon, Oliver!

charlie guevara, fingerlakes/US